In a cellular communication network based on orthogonal frequency division multiplexing (OFDM), a base station communicates with mobile stations that are within the base station's coverage by using signals that are orthogonal in frequency. Moreover, current third generation (3G) systems achieve a significant increase in throughput over second generation (2G) systems by taking advantage of multi-user diversity gain. That is, for point to multipoint systems such as forward link systems, all resources of a base station are dedicated to a single user (also referred to as a mobile station).
Whenever possible, a scheduler within the base station chooses the user with the best radio reception from among a set of users. If the set of users is large enough and if the channel fading of each user is independent, there is almost always a user with good radio reception. Consequently, the base station avoids the expense of sending information to a user with poor radio reception.
Furthermore, to facilitate mobility (the movement of a mobile station through a service area), a fast sector selection is employed. This technology allows the mobile station to quickly switch the transmission of data from one sector to another. It is important to realize that although the mobile station switches from sector to sector, the mobile station only receives a signal from only one sector.
For a mobile station at an edge of a cell (which is the boundary region between two or more sectors), even though the base station transmits to this mobile station with maximum power, the received signal is often received with very low power. As a result, this mobile station receives very poor radio reception and thus its data throughput is very low.
This has several effects on system performance. One effect is that if that particular mobile station requires a certain QoS, the base station must expend significant resources to serve this mobile station. The result of which is a significant decrease in total system throughput. Another effect is that the perceived user experience for that mobile station is very poor due to the fact that the data rate sustained with that link is very low. This is a significant issue because users expect to have the level of service regardless of where they are located in the sector.